The invention generally relates to image pick-up modules. More specifically, the invention relates to image pick-up modules for use in endoscopes or miniature cameras.
Without restricting generality, such an electronic image pick-up module is used in an endoscope, in particular in a flexible endoscope, the image pick-up module being arranged at the distal end of the endoscope shaft. Such an endoscope or video endoscope is disclosed, for example, in U.S. Pat. No. 5,754,313.
An image pick-up module generally comprises an electronic image sensor or image pick-up which converts light incident on it into an electrical signal. Such electronic image sensors are generally embodied using CCD or CMOS technology.
Miniaturized image sensors are currently available, of which those which have been produced using TAB (Tape Automated Bonding) technology are preferred. Such image sensors have contact fingers which are arranged in at least one row, usually in two rows on opposite sides of the image sensor, extend away from the image sensor approximately perpendicular to the light entry surface of the image sensor and are contact-connected to the circuit board of the image pick-up module. The contact fingers of an image sensor produced in TAB form are on the same plane as the image sensor. The contact fingers are bent over and are approximately perpendicular to the light entry surface of the image sensor only after they have been bent around.
In the sense of the present invention, a “circuit board” is understood as meaning both integral, single-part and multi-piece or multi-part circuit boards, particular ones of these designs being preferred in particular configurations, as also described below.
The circuit board (printed circuit board) is used not only to contact-connect the contact fingers of the image sensor but also to accommodate electronic components which are required for the control electronics and/or drive system of the image sensor.
A flexible multi-core cable which is used to guide the electrical video signals generated by the image sensor to the camera control unit and to supply drive and supply signals to the circuit board is also contact-connected to the circuit board.
The circuit board of an image pick-up module disclosed in the document DE 10 2004 056 946 A1 is of integral and rigid design and has the shape of a U, the U-shaped configuration being produced by milling material from a cuboidal or parallelepipedal circuit board blank. In accordance with the U-shaped configuration, this circuit board is open on two opposite longitudinal sides and closed on the remaining two opposite longitudinal sides. In the present description, “longitudinal direction” denotes the direction perpendicular to the light entry surface of the image sensor. Electrical components in a three-dimensional arrangement are contact-connected to the circuit board in that groove in the circuit board of the known image pick-up module which is formed by the U-shaped form, that is to say a plurality of electronic components are stacked on top of one another.
In this case, the multi-core flexible cable is contact-connected to the circuit board on the outer side of the circuit board which is remote from the image sensor and is referred to as the “underside” of the circuit board below. Although the known image pick-up module is very short in the longitudinal direction as desired, the contact-connection of the multi-core cable on the outer side of the circuit board which is remote from the image sensor has the disadvantage that the rigid part of the image pick-tip module, which is rigid overall, is extended in an undesirable manner by the cable assembly which has been contact-connected because the contact-connection points of the cores of the multi-core cable form a rigid arrangement which extends away from said outer side of the circuit board towards the proximal end.
In particular, when this image pick-up module is used in an endoscope having a flexible shaft, this results in the rigid distal beak part of the flexible endoscope being unfavourably extended. When the known image pick-up module is used, the rigid beak part of the flexible endoscope must be disadvantageously longer.
This known image pick-up module also has the disadvantage that the electronic or electrical components are arranged in the groove on top of one another rather than on one plane for reasons of space. As a result, a large amount of time and high costs are required when wiring the three-dimensionally arranged components and consequently when producing the entire image pick-up module.
DE-A-199 24 189 describes an image pick-up module whose circuit board is formed from a single-part plate which can be folded along flexible connecting sections and can be folded to form a parallelepipedal body having an essentially U-shaped cross section. When folded, the circuit board body has two sections, which extend essentially transversely to the image sensor and are spaced apart from one another, and a third section which runs essentially parallel to the image sensor, the image sensor being fitted to that end of the first and second sections of the circuit board body which is at a distance from the third section.
An image pick-up module disclosed in U.S. Pat. No. 5,754,313 has two separate circuit boards, the two circuit boards accommodating electronic miniature components and being used to contact-connect the cable or cable system which leads away. The two circuit boards run parallel to one another and approximately at right angles to the surface of the image sensor. The intermediate space between the two individual circuit boards is filled with a curable insulating filling composition and the multi-core cable is contact-connected on the outer sides of the two circuit boards. Both in the image pick-up module disclosed in DE 199 24 189 C2 and in the image pick-up module disclosed in U.S. Pat. No. 5,754,313, the circuit boards extend perpendicular to the image sensor, with the result that the circuit boards of these known image pick-up modules have a very long axial length which, as mentioned above, is undesirable, however.
The same applies to an image pick-up module which is disclosed in U.S. Pat. No. 5,857,963 and whose circuit boards or circuit board parts extend perpendicular to the image sensor. U.S. Pat. No. 5,220,198 discloses another image pick-up module which is comparable thereto and in which the circuit board is flexible and extends perpendicular to the image sensor.
U.S. Pat. No. 6,142,930 discloses an image pick-up module having a flexible circuit board, the cores of the multi-core cable being contact-connected on the outer side or underside of the circuit board which is remote from the image sensor, as a result of which the abovementioned disadvantages of the rigid part of the image pick-up module being extended exist.
Another disadvantage of all of the abovementioned image pick-up modules is the difficult assembly, that is to say the contact-connection of electronic components to the circuit board and the integration of electronic components on or in the circuit board.